1. Field of the Invention
This invention pertains to a locking mechanism which may be used on an agricultural machine which includes a retractable assembly connected to a fixed structure by means of at least one joint, said locking mechanism allowing one to immobilize said retractable assembly with respect to said fixed structure in at least one position by means of at least one elastic element and at least one stop element, and to release said retractable assembly by means of a special tool.
2. Description of the Related Art
Such a locking mechanism which can be used on an agricultural machine is known by those who are familiar with this area. This known locking mechanism includes a fixed support which is to be attached to the agricultural machine, which includes a latch which is used to immobilize the retractable assembly with respect to the fixed structure. This latch is connected to a fixed support of the locking mechanism by means of a pivot connection and a helical spring which constantly attempts to release the mechanism, that is to say it causes the latch to swing upward so as to allow the retractable assembly to retract.
In order to ensure locking of the retractable assembly with respect to the fixed structure, a lock is also provided which is used to hold the latch in its locked position. The lock is connected to the fixed support of the locking mechanism by means of a pivot connection with an axis perpendicular to that of the pivot connection of the latch. The lock is equipped with a helical spring which constantly attempts to bias the lock in locked position. The pivot connection which attaches the lock to the fixed support includes a screw, which is threaded into said latch and is connected to the fixed support.
Action on said screw, preferably by means of a special tool, causes the lock to pivot, thereby allowing the latch to be released. As soon as the lock has crossed a critical point, the latch automatically ejects the retractable assembly due to the effect of its helical spring, which then allows said lock to return to its initial position due to the effect of its spring, and after the operator has relaxed his action on the screw.
The operator then retracts the retractable assembly from this unlocked intermediate position into the final retracted position. In the unlocked position the latch remains open and the lock closed due to the effect of the respective helical springs which allow rapid locking of the retractable assembly and the fixed structure. The latch and the lock include relatively complex shapes so that at the time of locking the retractable assembly affects the latch and causes pivoting of the latter downward, which allows the lock to be opened.
At the end of this process the lock is closed automatically due to the action of its helical spring, and the retractable assembly is locked.
This locking mechanism has a certain number of disadvantages. For example, it has a large number of relatively complex parts, which translates into a relatively high cost.
On the other hand, the screw which allows one to control unlocking can be made easily accessible by hand according to placement of the locking mechanism on the agricultural machine and can, for this reason, be operated by hand alone if the springs are weak or worn out.
This known mechanism also has another disadvantage. As was already explained, once the retractable assembly is unlocked, the operator must retract, a second time, the retractable assembly from this intermediate unlocked position into the final retracted position, which presents a major risk. In effect, the operator may not carry out the operation of retraction after unlocking if his attention is diverted. In this case the retractable assembly may remaining in the unlocked intermediate position, which puts persons in the area in danger, when, for example, said retractable assembly is a protective device which encircles power-driven tools.